Personally I think that half the fun is finding and re-using junk second-hand
components and designing an amp around them.
I never realised that vacuum capacitors actually cost that much new, but when
suppliers sell to the military I think they just make up a number and move the
decimal point a few places to the right. That (and employing an army of
paper-pushing, otherwise-unemployable bottoms on seats to invent bureaucracy,
create Powerpoint slides and run Diversity courses) is where our taxes go....
I think my 3CX3000 amp must have cost me all of £500 or so including second
hand tubes and socket. At first I just assumed that being a half-Scottish
Yorkshireman it was just me that haggled over pennies at hamfest fleamarkets
and felt that I was on a mission to minimise pennies-per-watt, but when I sold
off a load of spare kit I realised that amongst Hams it's pretty much
endemic..... :-)
Cheers
Dave
G0OIL
There's a G-QRP Club. Was there ever a G-QRO club?
-----Original Message-----
From: "Jim Thomson" <Jim.thom@telus.net>
To: amps@contesting.com
Sent: 01/02/2010 07:19
Subject: [Amps] HB amps
<<<<<You can't really compare hamfest scrounged parts to brand new. Would
you buy an amp from Alpha if they told you all the parts were
scrounged from a hamfest?
When a person finishes their scrounged-part amplifier, they are
basically starting off with a used amplifier. I am not knocking used
amps, just wanting folks to be aware of what they are getting for
their efforts.>>>>>
## What would you like us to do, buy brand new Jennings /Comet
brand ceramic vac caps for both the tune + Load ??
## at $3-5 K each.. they are cost prohibitive new... which is why alpha
stopped
building the 77-dx. Surplus, they are a bargain. I picked up 4 x 12-500
pf @ 15 kv
ceramic vac caps [ Jennings] new , still in box's.. and all hi-pot test well
over 15 kv.
## I also picked up [nib] 2 x 10-1000pf @ 15 kv ceramic Jennings caps.. and
these are motor driven.
also got a 25-1000 pf @ 15 kv, non motor driven [ measures 17-1056 pf]
## as for vac load caps, I managed to get a pair of Jennings 50-4000 pf @
5 kv ceramic caps,
and 1 x 50-3000 pf @ 5 kv Jennings. Fair radio had NIB 50-2000, and also
50-2300 pf @ 10 kv
glass vac caps. The glass ones are padded on 160m.. with paralleled NPO 5
kv ceramic doorknobs [HEC HT-50/58]
8-10 x 100-160pf
## 15-25-50' rolls of cu tubing is cheap at home depot, lowes, etc. Just
cuz Alpha uses undersized 3/16"
tubing on 20-10m doesn't mean you have to. [ I use 1/2".. then I silver plate
all of it]
## Commercial ham amps will use every trick in the book to avoid the use of
vac caps, etc.
## IMO... after doing this since 1972... I have come to the conclusion
that's its just as easy to build a big amp..as a small one.
## IF you don't have enough HP under the hood of your truck, you don't
install a 2-4 engines under the hood.... you get a bigger engine to start with!
## why mess with 2-4 tubes.... 2-4 sockets.... 2-4 chimney's.... 2-4
parasitic suppressor's, 2-4 anode connector's
then cross ur fingers and hope the [A] drive splits 2-4 way's... and [B]
the 2-4 tubes match up...
and [C] airflow splits 2-4 ways, etc, etc ??
## A single $200.00 YC-156 is simple. NO socket required... just whack
a hole in the chassis,
and bolt the integral grid flange to the chassis. NO parasitic suppressor
required either. [ no anode connector either]
## The mating SK-306 chimney is a dime a doz. Fil requirements are
miniscule.
## tuned input is simple. PI net is simple... and uses vac caps..... [and so
does my 2 x 4-1000 amp I built yrs ago.]
## 1 cubic ft, 120 lb hypersil pole pigs are also a dime a doz. [4160/4800
variety] .
## 1 kv-6A [400 A surge] 6A10 diodes [ big bro to the 1N5408] are cheap
in bulk... mouser.
## 2300-2500-3900 uf @ 450 vdc electrolytics are available NIB, surplus,
have 10A ripple current ratings,
and provide for < 1% ripple... and superb dynamic B+ regulation. NIB,
surplus contactors are easily
available.
## don't like the loaded Q for the tuned input / high powered PI net
output... then re-tap the coil and change it.
## Once your all done.... you end up with an amp that makes the Alpha 77-SX +
Henry 8-K.... both look
like sick puppies. The re-sale value is also high. Blower noise ? Put
it in another room, and simply run in there
and ..'dial up the pre-set's. Once tuned for say 14.200 , it's good from
14.100 to 14.300 I can't squeeze
1 more watt out of it, if I try and re-tune at either 14.1.... or 14.3 [
assumes ant has flat swr across the same 200 khz]
## Trying to compare commercial made ham amps to hb ham amps is sorta like
apples and oranges. The HB builder, is at
liberty to use anything, and everything, at his disposal. He can choose to cut
corner's.. or not. He can also up-grade any portion
at any time... and after the fact. He's not trying to enhance profits. AL
plate can be polished to a high luster, like a mirror,
or chrome, or leave it plane, or do a brushed finish, like stereo amps from
the 70's. See where I'm going with this?
later........ Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|